Reports code that always produces the same result, throws an exception, or may violate nullability contracts.

Examples:

if (array.length < index) {
  System.out.println(array[index]);
} // Array index is always out of bounds

if (str == null) System.out.println("str is null");
System.out.println(str.trim());
// the last statement may throw an NPE

@NotNull
Integer square(@Nullable Integer input) {
    // the method contract is violated
    return input == null ? null : input * input;
}

Use the inspection options to fine-tune annotation processing policy and adjust the list of situations that should be checked.